Epilepsy is a common neurological disorder often resulting in considerable disability over many years of a patient's life. The most effective treatment in the majority of patients is the use of various anticonvulsant agents. There is marked variability of the metabolism of the anticonvulsants from patient to patient. A dosage regimen considered therapeutic may result in considerable slowing of mental performance. Our investigative work includes: 1. Clinical determination of the most effective therapeutic regime, 2. Chemical determination of plasma levels of the anticonvulsants and their metabolites, 3. Turnover studies of these medications and their metabolites utilizing non-radioactive labelled anticonvulsants, 4. Use of special testing procedures to determine changes in patient's mental performance with variation of their therapeutic regimen. BIBLIOGRAPHIC REFERENCE: Whyte, M.P., and Dekaban, A.S.: Metabolic fate of phenobarbital: A quantitaitve study of p-hydroxyphenobarbital elimination in man. Drug Metabolism and Disposition, 5: 63-70, 1977.